Radar directional antenna assembly



July 12, 1960 H. KLAUSER 2,945,229

RADAR DIRECTIONAL ANTENNA ASSEMBLY Filed Oct. 10, 1956 2 Sheets-Sheet 1July 12, 1960 KLAUSER 2,945,229

RADAR DIRECTIONAL ANTENNA ASSEMBLY Filed Oct. 10, 1956 2 Sheets-Sheet 2United States Patent RADAR DIRECTIONAL ANTENNA ASSEMBLY Hans Klauser,Zurich, Switzerland, assignor to Albiswerk Zurich A.G., Zurich,Switzerland, a Swiss corporation Filed Oct. 10, 1956, Ser. No. 615,141

Claims priority, application Switzerland Oct. 28, 1956 12 Claims. (Cl.343-754) This invention relates to a directional antenna system forradar. It particularly concerns a system in which a primary radiatorcircles about the focal point of a reflector, the latter beingindependently reciprocated, preferably in a plane.

For producing a sharp and narrow directional radar beam that can bedirected at any point in space, the directional antennas in usegenerally comprise a primary radiator and a reflector which arerotatable together about a vertical axis and are tiltable about ahorizontal axis. In some cases the entire radar system is mounted forrotation about a vertical axis and only the appertaining directionalantenna is tiltable in a vertical plane.

Aside from the necessity for aiming the directional antenna at a targetpoint at any lateral and elevational angle, there sometimes arises theproblem of imparting to the directional beam an additional movement,preferably a rapid one. For example, for the automatic tracking oftargets, the directional antenna is usually caused to perform anadditional scanning movement by employing a rotating directional beamdeflected away from the symmetry axis of the reflector. Furthermore, insuch installations it may sometimes be preferable to provide for thepossibility of a search limited to a small angular space sector. This isuseful in the event of inaccurate target information or lack of targetinformation. Such additional searching movement is performed, forinstance, by rapid to and fro, or upward and downward, movement of thedirectional beam in a vertical plane simultaneously with a slow changein the lateral angle of the directional antenna.

The present invention, in a more specific aspect and preferredembodiment, relates to a directional radar antenna assembly, generallyof the above-mentioned kind, in which a primary radiator and areflector, having a rotationally symmetrical surface, are operated toselectively execute a scanning movement by means of a directional beamwhich rotates about and is deflected away from the symmetry axis of thereflector and to carry out a searching movement by means of adirectional beam which performs a back and forth movement within aplane.

Numerous directional antenna systems have become known which, inaddition to the lateral and elevational motion of the antenna, afford anadditional scanning or searching movement of the directional beam, inthe abovementioned sense. There are also directional antenna systemswhich selectively permit a scanning as well as a searching movement ofthis kind. In one of the known systems, of the last-mentioned type, twoseparate antennas are provided, one being designed for an additionalscanning movement and the other for an additional searching movement.The relatively great space requirements, and also the greater weight, asWell as the necessary switching from one to the other antenna are themore obvious disadvantages of such a twin system. According to anotherproposal, in which a single antenna is used for both the scanning asWell as for the searching movement, the

Patented July 12, 1960 entire antenna is placed in motion, the scanningmovement being effected by rotation of the antenna with the antenna axisdeflected relative to the axis of rotation, whereas the searchingmovement is effected by tilting the antenna within a plane. In this casethe moving masses are relatively large so that, because of the desiredgreat velocities, considerable forces of acceleration are required forperforming these movements. Similar conditions obtain with another knowndirectional antenna system in which the entire antenna is reciprocableabout a vertical axis and the reflector is additionally tiltable about ahorizontal axis relative to the primary radiator. In this case,furthermore, the means for producing the mentioned scanning movement aremore complicated since the antenna reciprocation along a circular arcmust be formed of two linear components of motion. These are alsodirectional antenna systems in which the reflector as well as theprimary radiator are additionally movable and which, when in operation,are kept in motion simultaneously, so that by choice of respectivelydiflerent velocities for the motion of the reflector on the one hand andthe primary radiator on the other hand, different relative motions canbe brought about. For example, by employing a rotating reflector havingits symmetry axis at an angle to the axis of rotation, and by furtherutilizing a primary radiator which circularly reciprocates about thesame axis of rotation, it is possible to produce, merely by suitablechoice of the velocity ratio, a directional beam which either movesforward and back within a plane, or moves in a cycloidal path. Althoughin this manner the directional beam can be made to follow a greatvariety of patterns, the expenditure required for the mechanicalelements required to drive the reflector and the primary radiator isuneconomical and undesirable for a simple scanning and searching motion.This is especially so if, aside from the mentioned movements, thepossibility of varying the degree of deflection must be provided for.This is the case if a deflection of the beam of about 1 is chosen forthe scanning movement, whereas the searching movement is to cover atilting range of about :10".

It is a more specific object of my invention to readily permit such adifferentiation between the respective beam deflections for scanningmovement and searching movement of the directional beam with the aid ofequipment of relatively simple design and little space requirement, ascompared with the known systems mentioned in the foregoing.

To this end, and in accordance with my invention, I provide a radardirectional antenna system which comprises a primary radiator circularlymovable about the focal point of the reflector, preferably in a planeperpendicular to the axis of symmetry of the latter. The reflector ismovable about an axis perpendicular to its axis of symmetry, thesymmetry axis of the reflector being coincident with the axis ofrotation of the primary radiator in the position of rest of thereflector, that is, when the latter is not reciprocating. In thissystem, the circular movement of the primary radiator with the reflectorat standstill performs the above-mentioned scanning movement. Thereciprocating motion of the reflector, for example with the primaryradiator at standstill, performs the above-mentioned searching motion ofthe directional beam. By combining the two antenna operating principlesinto a single system, not only are the advantages inherent in theindividually known principles retained, but in addition there resultsthe elimination of the above-mentioned disadvantages of the antennadevices heretofore available for performing an additional searchingmotion as well as an additional scanning motion of the directional beam.

These specific objects, advantages and features of the invention will bemore fully understood from the following description of a preferredembodiment of the radar 3 antenna assembly and from the accompanyingdrawing, in which:

Fig. 1 is a schematic view of the assembly, the angles on and {3 beingexaggerated to lend clarity; and

Fig. 2 is a detailed view, seen from above, of part of an antennaassembly, of a modified form.

The initial part of the following description has reference to Fig. 1.

A primary radiator 1 is mounted in front of a rotationally symmetricalreflector 2, which is parabolic for example, and which is mounted on ahousing structure 3. The latter encloses the drive means employed forimparting additional movement to the primary radiator 1 and to thereflector 2. The housing 3 is mounted on a standard 4 and is tiltableabout a horizontal shaft 5 journaled in the standard. The standard 4 ismounted on a base 6 and is rotatable with respect thereto about avertical shaft 7. Driving power for the rotational movement of thestandard 4 and for the tilting movement of the housing 3 is suppliedfrom respective electric motors 8 and 9 through respective worm gears 10and 11. By means of these drives, the housing 3, which determines theposition of the main axis 12 of the antenna, can be adjusted relative tothe lateral angle and relative to the elevational angle.

The primary radiator 1 is mounted on the front end of a wave-guideconductor 13 of linear shape. The conductor 13 is universally pivotedfor motion in all angular directions by means of a universal pivot 140fixed thereon and mounted in bearing 14, which is located behind thecrest point of the reflector 2 and is carried by housing 3. The rear endof the conductor structure 13 is articulately linked, at universal pivot130, with a driving disc 15 in eccentric relation to the drive shaft 160of a motor 16 so that the axis 17 of the wave-guide structure 13, duringoperation, defines a circular cone. During such motion, the primaryradiator 1 moves in a circle about the main axis 12, but has no rotarymotion about the conductor axis 17. The number of rotations about mainaxis 12 per minute may, for example, be about 1,800, and the angle atbetween conductor axis 17 and main axis 12 may be, for example, about 1to 1.5 The supply of HF power, not illustrated, to the wave-guidestructure 13 is preferably eflected in the vicinity of the universalpivot bearing 14. Motor 16 is mounted on housing 3.

The reflector 2, and its support 200, is likewise tiltable about thecenter of the pivot bearing 14 carried by housing 3. It is journaledindependently of the waveguide structure 13, by means of bearing 141acting on pivot 140, for tilting motion about an axis perpendicular tothe axis of symmetry of the reflector, the axis of tilt in theillustrated example extending in the horizontal direction. The tiltingmovement of the reflector is effected by means of a mechanical resonancedrive. For this purpose point 18 on support 200 of the reflector 2 isconnected with a crank wheel 20 through a driving spring 19. The crankwheel 20 is driven by a motor 21, which is mounted on housing 3, througha worm gear 22. The mechanism is further provided with oscillatorsprings 23 and 24 which are respectively connected between housing 3 andpoints 18 and 180 on reflector support 200 and which are so chosen thatthe natural frequency of the oscillating system formed by the reflector2, support 200, and the springs 23, 24 is in the range of about 3 to 5cycles per second. In the rest position of the reflector its axis ofsymmetry is to be coincident with the rotational axis of the primaryradiator 1, which is main axis 12 of the antenna. Main axis 12 is themedian position of the symmetry axis of the reflector 2. The tiltingrange denoted by the angle 5 between main axis 12 and the symmetry axis25 or 25' of the deflected or tilted reflector (shown by dot and dashlines) may, for example, be about i10. For better illustration, the twoangles a and p are shown on the drawing larger than the above-mentionedvalues. It is understood that pivot is ofiset sufliciently toaccommodate angle a.

The above-described radar directional antenna according to the inventionpermits the performing of the above-mentioned additional motions, namelyscanning motion and searching motion, selectively and independently ofeach other. By circular motion of the primary radiator 1 about the mainaxis 12 with the reflector 2 at standstill a directional beam isproduced which is deflected out of the symmetry axis of the reflectorand which rotates about this axis. By imparting tilting motion to thereflector 2 with the primary radiator 1 at standstill, a directionalbeam is issued which moves up and downwardly. For each of the twoadditional motions of the directed beam only part of the antenna systemis placed in motion so that the required driving means can be givenrelatively small weight and size. Of particular advantage in thisrespect is the fact that during searching motion of the beam thereflector, for a given deflecting angle of the beam, need be tilted onlyone-half the amount of this angle. It is understood that reflector 2 hasa sufficiently wide aperture at 201 to give freedom of relative movementto conductor 13 over the angle 25.

Fig. 2 departs, in a few details, from Fig. 1. In Fig. 1 support 200 ofthe reflector 2 is pivotally mounted, by means of universal joint member141 aflixed thereto, about pivoting element which is mounted upon theextension of the Wave guide structure 13. Whereas in Fig. 2 thereflector supports 200 are pivoted on axles 50 which are mounted in thesides of the block or housing structure 3'. The tilting movement of thereflector 2 of Fig. 2 is obtained by the same type of mechanicalresonance drive that is employed in Fig. 1. For example, at a point onreflector 2 mid-way between the two supporting arms 200, and below thehorizontal plane through axles 50, and also below the wave guide andradiator driving means, a driving compression spring, not illustrated,similar to spring 19 is attached. A motor and crank wheel, notillustrated, like that shown in Fig. 1, are provided to oscillate thereflector 2 about pivots 50. Two springs, not illustrated, which aresimilar to springs 23 and 24, serve to bias the reflector, and its axisof symmetry, toward the rest or median position. These two springs areattached at one end to the housing 3' and, at the other end, to thereflector 2. One, for example, is attached at the point of attachment ofthe driving spring, the other being attached at a point on the reflectorwhich is below the pivots 50.

Elements in Fig. 2 which correspond to those of Fig. 1 arecorrespondingly numbered. The primary radiator 1 of Fig. 2 is energizedthrough a wave-guide system composed of a stationary portion and amovable portion. The movable portion consists of a straight tubularwaveguide conductor 13 whose longitudinal axis is indicated at 17, andof a part 131 coaxially fixed thereon having a conical stern 132 uponthe free end of which radiating element 1 is mounted. The other end ofconductor 13 passes freely through apical aperture 201 in the reflector2, and through boss 300, which is fixed upon wall 301, and then passesinto the driving block 3'. Fixedly and coaxially attached to the innerend of conductor 13 is a hollow coupling sleeve 302, to which is fixedlyand coaxially attached a turning arm 303 carrying a balancing mass 304.On the free end of the latter is a universal ball pivot element 130which is carried in an off-center socket in eccentric 15. The latter isrotated about the axis of symmetry 12 of the reflector 2 by motor 16acting through gears 161 and 162.

The movable coupling sleeve 302, together with the stationary portion305 of the waveguide system presents the well-known waveguide-universaljoint. This movable joint is of the choke-coupling type and consists ofcircular flange 306 and ring 307, both terminating the hollow cavity308. Circular flange 306 does not contact ring 307 electro-conductively.These parts are sepafated by a small circular gap 309, which provides apassage to permit gas pressure in the sealed housing 3' to be applied tothe hollow interior of conductor elements 13, 131, 132 as described in apending application Serial No. 608,742 filed on Sept. 10, 1956 by L.Reinhard and H. Klauser. A ring gasket 40 seals the wall 301 to themovable coupling sleeve 302. The latter is journalled in the wall 301 bya Cardan-joint. This joint comprises outer ring 44 which is fixed withinan annular flange seat 310 on wall 301, and an inner ring 45 fixedly setupon the coupling sleeve 302. There are two pairs of pivot pins 46, onepair being shown. Each pair has its axis perpendicular to that ofthe'other pair, thus providing two diametrically opposite pivots, onepair being mounted on the outer ring 44, the other pair on the innerring 45. A movable ring 47 located between rings 44 and 45 carries andarticulates four ball bearing rollers 48, two being shown. The innerraces of the ball bearing rollers are seated upon respective pivot pins.

In the preferred operation the motor 21 (Fig. 1) turns crank 20 toreciprocate spring 19. at the natural frequency of the entireoscillatory system of the reflector.

Although all four possible displacements of the antenna can be carriedout simultaneously, the simulta neous tilting of housing 3, and itsturning, together with the described movements of the primary radiatorand the reflector, has no practical advantage, for the instant purposes.For this reason, the above description refers to the rest position ofthe parabolic reflector, the preferred operation being with the pivot ofthe reflector at rest.

The signifiance of the frequency range of 3 to 5 cycles per second ofthe resonance drive is as follows: At antenna motion frequencies below 3c.p.s. no resonance drive is required. A simple driving device whichpositively or constrainedly drives the antenna is sufiicient, becausethe forces of acceleration can be kept relatively small. The advantagesof the resonance drive make themselves felt, relative to rigid orconstrained drives, only, or principally, when the antenna-motionfrequency exceeds 3 c.p.s. The desire to have the searching movement ofthe antenna occur as rapidly as possible is, on the other hand, limitedby the fact that a satisfactory echo pulse or tip can be produced on theradar screen only if the target is illuminated sufliciently long by theradar beam. Consequently the lateral velocity of the laterally displaceddirectional radar beam must, to obtain a given impulse energy, a givenfrequency of the succession of pulses, and a given width of thedirectional beam, and for given sizes of the target, not exceed acertain limit value. In view of these limitations, in radar devices ofthe type described in the application, the largest frequency ofsearching movement permissible in the most favorable case isapproximately 5 c.p.s.

It will be understood by those skilled in the art, upon a study of thisdisclosure, that, with respect to constructional devices, the inventionpermits of a great variety of modifications and may be embodied indevices other than the one particularly illustrated and described,without departing from the essential features of the invention, andwithin the scope of the claims annexed hereto.

I claim:

1. A radar directional antenna apparatus comprising a mechanical system,a radar-beam reflector forming part of the system, the reflector havingan apertured apex, a focal point, and an axis of symmetry passingthrough the apex and focal point, means for oscillating the reflectorabout a point behind the reflector, the oscillation being such that thesaid axis moves upwardlydownwardly in a plane, a wave guide conductorwhich passes through the apertured apex, a primary radiator mounted uponthe forward end of the conductor, pivot means for the conductor which isbehind the reflector,

independent means for moving the conductor on its pivot to move theradiator about the focal point of the reflector independently of thesaid oscillation of the reflector, pivoted support structure for saidsystem, and means to turn the support structure about two perpendicularaxes.

2. A radar directional antenna system comprising a first supportingstructure, first pivot means for the said structure, first drive meansto turn said structure about the axis of the first pivot means toprovide a generally horizontal traverse, a second supporting structurepivoted to the first supporting structure on second pivot means forupward and downward movement about an axis transverse to the pivot axisof the first supporting structure, second drive means to so move thesecond supporting structure about the transverse axis, third pivot meanscarried by the second supporting structure, a wave guide conductorpivotally mounted by the third pivot means, a primary radiator mountedon the front portion of the wave guide conductor, third drive means tomove said conductor on said third pivot means in a direction generatinga conoidal surface, whereby the primary radiator circles about an axis,a symmetrical reflector independently pivoted upon the second structurefor upward and downward tilting movement, the said rotation of theprimary radiator effecting substantially a circling about the focalregion of the reflector when the latter is not oscillating, fourth drivemeans for tilting the reflector upwardly and downwardly about its pivot,each of the four drive means being independently operable, whereby thecircling of the primary radiator is performable, but not exclusively so,with the reflector not oscillating, and the upward and downward tiltingof the reflector is performable, but not exclusively so, with theprimary radiator not circling.

3. A radar directional antenna system comprising a first supportingstructure, first pivot means for the said structure, first drive meansto turn said structure about the axis of the first pivot means toprovide a generally horizontal traverse, a second supporting structurepivoted to the first supporting structure on second pivot means forupward and downward movement about an axis transverse to the pivot axisof the first supporting structure, second drive means to so move thesecond supporting structure about the transverse axis, third pivot meanscarried by the second supporting structure, a wave guide conductorpivotally mounted by the third pivot means, a primary radiator mountedon the front portion of the Wave guide conductor, third drive means tomove said conductor on said third pivot means in a direction generatinga conoidal surface, whereby the primary radiator circles about an axis,a symmetrical reflector independently pivoted upon the second structurefor upward and downward tilting movement, the said rotation of theprimary radiator effecting substantially a circling about the focalregion of the reflector when the latter is not oscillating, fourth drivemeans for tilting the reflector upwardly and downwardly about its pivot,each of the four drive means being independently operable, whereby thecircling of the primary radiator is performable, but not exclusively so,with the reflector not oscillating, and the upward and downward tiltingof the reflector is performable, but not exclusively so, with theprimary radiator not circling, the symmetry axis of the reflector beingcoincident with the axis of said circling of the primary radiator whenthe reflector is in median position with respect to said tiltingmovement thereof, the circular motion of the primary radiator being notless than about 1,000 rotations per minute, the angle between thelengthwise axis of the conductor and symmetry axis of the reflectorbeing not more than about 1.5 degrees.

4. A radar directional antenna system comprising a first supportingstructure, pivot means for the said structure, first drive means to turnsaid structure about the axis of the pivot means to provide a generallyhorizontal traverse, a second supporting structure pivoted to the firstsupporting structure on second pivot means for upward and downwardmovement about an axis transverse to the pivot axis of the firstsupporting structure, second drive means to so move the secondsupporting structure about the transverse axis, universal pivot meanscarried by the second supporting structure, a wave guide conductorpivotally mounted by said universal pivot means, a primary radiatormounted on the front portion of the wave guide conductor, third drivemeans to move said conductor on said universal pivot means in adirection generating a generally conoidal surface, whereby the primaryradiator circles about an axis, a symmetrical reflector independentlyjournalled by said universal pivot means, the said circular motion ofthe primary radiator being substantially about the focal region of thereflector, fourth drive means for tilting the reflector upwardly anddownwardly about said universal pivot means, each of the four drivemeans being independently operable.

5. A radar directional antenna system comprising a symmetrical reflectorand a primary radiator mounted for circular motion about an axis, thecircular motion being about the focal point of the reflector in a planeperpendicular to the axis of symmetry of the reflector, the reflectorbeing mounted for reciprocating movement about an axis perpendicular toits axis of symmetry, the symmetry axis of the reflector beingcoincident with the axis of said circular motion of the primary radiatorwhen the reflector is not carrying out said reciprocating movement, thesaid circular motion of the primary radiator with the reflector atstandstill performing a scanning movement, the said reciprocatingmovement of the reflector being operable with the primary radiator atstandstill to carry out a searching movement of the directional beam,and means for turning the primary radiator and the reflector togetherabout coordinate axes.

6. A radar directional antenna system comprising a first supportingstructure, first pivot means for the said structure, first drive meansto turn said structure about the axis of the first pivot means toprovide a generally horizontal traverse, a second supporting structurepivoted to the first supporting structure on second pivot means forupward and downward movement about an axis transverse to the pivot axisof the first supporting structure, second drive means to so move thesecond supporting structure about the transverse axis, third pivot meanscarried by the second supporting structure, a wave guide conductorpivotally mounted by the third pivot means, a primary radiator mountedon the front portion of the wive guide conductor, third drive means tomove said conductor on said third pivot means in a direction generatinga conoidal surface, whereby the primary radiator circles about an axis,a symmetrical reflector independently pivoted upon the second structurefor upward and downward tilting movement, the said rotation of theprimary radiator effecting substantially a circling about the focalregion of the reflector when the latter is not oscillating, fourth drivemeans for tilting the reflector upwardly and downwardly about its pivot,each of the four drive means being independently operable, whereby thecircling of the primary radiator is performable, but not exclusively so,with the reflector not oscillating, and the upward and downward tiltingof the reflector is performable, but not exclusively so, with theprimary radiator not circling, the symmetry axis of the reflector beingcoincident with the axis of said circling of the primary radiator whenthe reflector is in median position with respect to said tiltingmovement thereof.

7. A radar directional antenna apparatus comprising a mechanical system,said system including structure means mounted for tilting about a mainlyhorizontally directed axis, a radar-beam reflector forming part of thesystem, the reflector having an apertured apex, a focal point, and anaxis of symmetry passing through the apex and focal point, means forpivotally mounting the reflector upon the said structure means andpower-driven means for automatically oscillating the reflector about apoint behind the reflector independently of and without moving the saidstructure means, the oscillation being such that the said axis moves ina plane, a wave guide conductor which passes through the apertured apex,a primary radiator mounted upon the forward end portion of theconductor, universal pivot means for mounting the conductor on thestructure means, the pivot means being behind the reflector, independentmeans for moving the conductor on its pivot means to move the radiatorabout the focal point of the reflector, whereby the primary radiator canbe so moved while the reflector is not subjected to said oscillation.

8. A radar directional antenna apparatus comprising a mechanical system,said system including structure means mounted for tilting about a mainlyhorizontally directed axis, a radar-beam reflector forming part of thesystem, the reflector having an apertured apex, a focal point, and anaxis of symmetry passing through the apex and the focal point, means forpivotally mounting the reflector upon the said structure means, andpower-driven means for automatically oscillating the reflectorindependently of and without moving the said structure means, about apoint behind the reflector, the oscillation being such that said axismoves upwardly-downwardly in a plane, an extended wave guide conductorwhich passes through the apertured apex, a primary radiator mounted uponthe forward end portion of the conductor, universal pivot means formounting the conductor on the structure means, which pivot means isbehind the reflector, independent means for moving the conductor on itsuniversal pivot to describe a cone and circle the radiator about thefocal point of the reflector when the reflector is not oscillating.

9. A radar directional antenna apparatus comprising a mechanical system,said system including a structure mounted for tilting about a mainlyhorizontal axis, a radar-beam reflector forming part of the system, thereflector having a focal point and an axis of symmetry passing throughthe focal point, means for pivotally mounting the reflector upon thesaid structure and for automatically oscillating the reflectorindependently of and without moving said structure, the oscillationbeing such that the said axis is displaced upwardly-downwardly, a waveguide conductor, a primary radiator mounted upon the conductor, meansoperable independently of the re flector oscillating means for movingthe conductor to cause the radiator to circle about the focal point ofthe reflector when the reflector is not oscillating, the oscillation ofthe reflector being performable with the primary radiator at standstilland also with the primary radiator in motion.

10. A radar directional antenna apparatus comprising a mechanicalsystem, said system including a structure mounted for tilting about amainly horizontal axis, a radar-beam reflector forming part of thesystem, the reflector having a focal point and an axis of symmetrypassing through the focal point, means for pivotally mounting thereflector upon the said structure and for automatically oscillating thereflector independently of and without moving said structure, theoscillation being such that the said axis is displacedupwardly-downwardly, a wave guide conductor, a universal pivot means forthe conductor, a primary radiator mounted upon the conductor,power-driven means operable independently of the reflector oscillatingmeans for moving the conductor on its universal pivot means to cause theradiator to circle about the focal point of the reflector when thereflector is not oscillating, the said circling of the radiator being atleast about 1000 revolutions per minute, the oscillation of thereflector being performable with the primary radiator at standstill andalso with the primary radiator in motion.

11. A radar directional antenna apparatus comprising a mechanicalsystem, said system including structure means mounted for tilting abouta mainly horizontal axis, a radar-beam reflector forming part of thesystem, the

reflector having a focal point and an axis of symmetry passing throughthe focal point, means for pivotally mounting the reflector upon thesaid structure and for automatically oscillating the reflectorindependently of and without moving said structure means, theoscillation being such that the said axis is displacedupwardlydownwardly, a wave guide conductor, universal pivot means formounting the conductor on said structure means, a primary radiatormounted upon the conductor, power-driven means operable independently ofthe reflector oscillating means for moving the conductor on theuniversal pivot means to cause the radiator to circle about the focalpoint of the reflector when the reflector is not oscillating, the meansfor oscillating the reflector comprising a resilient mechanicalresonance drive and reflector constraint system, the drive beingoperative to oscillate the system at its natural mechanical frequency,the oscillation of the reflector being performable with the primaryradiator at standstill and also with the primary radiator in motion.

12. A radar directional antenna apparatus comprising a mechanicalsystem, said system including a structure mounted for tilting about amainly horizontal axis, a radar-beam reflector forming part of thesystem, the reflector having a focal point and an axis of symmetrypassing through the focal point, means for pivotally mounting thereflector upon the said structure and for automatically oscillating thereflector independently of and without moving said structure, theoscillation being such that the said axis is displacedupwardly-downwardly, a wave guide conductor, universal pivot means forthe conductor, a primary radiator mounted upon the conductor, meansoperable independently of the reflector oscillating means for moving theconductor on its universal pivot to cause the radiator to circle aboutthe focal point of the reflector when the reflector is not oscillating,the means for oscillating the reflector comprising a resilientmechanical resonance drive and reflector constraint system, the drivebeing operative to oscillate the system at its natural mechanicalfrequency, the mechanical resonance drive and reflector systemcomprising three springs operatively connected to the reflector, onebeing a driv; ing spring, mechanical means connected to the drivingspring to alternately place it in compression and tension, and two beingsprings which restore the reflector to a median position, theoscillation of the reflector being performable with the primary radiatorat standstill and also with the primary radiator in motion.

References Cited in the file of this patent UNITED STATES PATENTS2,543,188 Moseley Feb. 27, 1951 2,574,376 Childs et al. Nov. 6, 19512,713,121 Lyman July 12, 1955 FOREIGN PATENTS 1,082,071 France June 16,1954

